1. Field of the Invention
The present invention relates to a method and a system for examining the shooting direction of a camera apparatus mounted on a vehicle like a automobile and to a structure for mounting an onboard camera apparatus using a mounting plate.
2. Description of the Related Art
Much attention is given in recent years to an outside view monitoring system using a single-lens camera or a stereo camera apparatus as a preview sensor. This kind of monitoring system photographs a forward view of own vehicle by an onboard camera apparatus attached to the vehicle and recognizes traffic conditions ahead of own vehicle based on photographed images using image-recognition technology (also using the principle of triangulation in a stereoscopic method). Then, when the need arises, the monitoring system calls a driver's attention or performs vehicle behavior control operation such as deceleration by a downshift.
When this kind of monitoring camera apparatus is fitted to a vehicle body, a high degree of accuracy is needed with respect to its mounting position. This is because an error in the mounting position of the camera apparatus results in a deviation of the shooting direction of the camera apparatus, eventually causing a reduction in the reliability of monitoring control operation. Especially when a stereo camera apparatus is used as an onboard camera apparatus, an extremely high degree of accuracy is needed with respect to its shooting direction. This is because a deviation of the shooting direction directly affects a calculated distance, since the distance is calculated from parallaxes between a pair of photographed images in the stereoscopic method. In actuality, however, variations occur in the shooting direction of individual onboard camera apparatus due to distortion of vehicle bodies themselves or limitations in the accuracy of camera installation. Thus, when the shooting direction deviates, a technique for making a fine adjustment is used to make up for the deviation of the shooting direction equivalently by applying an image transformation, such as affine transformation, to the photographed images.
A finely adjustable range achieved by such an image transformation is not so wide, however. Therefore, when the shooting direction of an onboard camera apparatus greatly deviates from a proper range (i.e., a range for which fine adjustment by the affine transformation, for example, is possible), it becomes difficult to adjust to make up for the deviation by an image transformation. It is therefore necessary to examine whether the shooting direction of each camera apparatus installed falls within the proper range in a test process performed upon completion of its installation. Samples which have been judged to be deviating from the proper range need to be subjected to mechanical readjustment, such as re-installation of the camera apparatus, so that their shooting directions would fall within the proper range. For this reason, it is strongly desired to establish a test method which makes it possible to achieve improved efficiency and automation of such testing.